The present invention relates to a developer material supplying device, and more particularly, to a dry type developer material supplying device for use in an electrophotographic type image recording apparatus such as a copying machine, a printer and a facsimile.
A Karlson type electrophotographic type processing unit has conventionally been used in an image recording apparatus. As shown in FIG. 1, the processing unit 1 generally includes a photosensitive drum 2, a primary charger 3, a developing unit 5, and a cleaning unit 10. The photosensitive drum 2 serves as a latent image carrier, and the primary charger 3 is adapted for uniformly charging the photosensitive drum 2. An opening 4 is formed at an outer frame la of the processing unit for introducing light from a light source (not shown) and modulated by image signals and for scanning the modulated light onto the photosensitive drum 2 for forming an electrostatic latent image thereon as indicated by an arrow A in FIG. 1. The developing unit 5 is adapted for providing a visible developer toner image corresponding to the latent image on the drum 2. To this effect, developer toners 8 are accumulated in the unit 5, and a developing roller 6 and a blade 7 are provided. The developing roller 6 is adapted for providing developer toners on the photosensitive drum 2, and the blade 7 is adapted for regulating a, thickness of the developer toners to be formed on the drum 2. The image recording apparatus (not shown) to which the processing unit 1 is assembled is provided with a transferring charger 6 for transferring the developer toner image on the photosensitive drum 2 onto a printing sheet (not shown). In this case, residual developer toners may be remained on the photosensitive drum 2. Therefore, the cleaning unit 10 scrapes the residual toner from a surface of the drum 2 and collects the thus scraped toners 9 in the cleaning unit. The cleaning unit 10 has a waste toner container 11.
Apparently, in accordance with the numbers of the image recording operation, developer toners 8 in the developing unit 5 are gradually consumed. On the other hand, residual toners on the drum 2 is gradually accumulated in the waste toner container 11 of the cleaning unit 10. Further, the photosensitivity and chargeability of the photosensitive drum 2 may be gradually degraded in accordance with the repeated image recording operation. In this connection, these expendable must be replaced with a new one or must be supplemented at every given numbers of image recording operation. Thus, recently, a so called integral type processing unit is widely available in which the above described various components and units are integrally housed in a one unit in order to facilitate replacement work and to avoid leakage of the developer toners at the time of the replacement work.
The integral type processing unit is designed such that service life of the photosensitive drum 2, used-up period of the developer toners 8 in the developing unit 5 and the fully accumulating period of the wasted toners 9 in the cleaning unit 10 are approximately coincident with one another. Obviously, the used-up period of the toner 8 is determinative by an internal volume of the developing unit 5, and fully accumulating period of the wasted toners 9 is determinative by an internal volume of the container 11. If these units reach their service lives, a new processing unit is assembled into the image recording apparatus instead of the old processing unit to facilitate the replacement work thereof.
However, the integral type processing unit incurs problems because of the improvement in the photosensitive drum 2. That is, according to a recent improvement in an organic photosensitive compound (OPC) as the photosensitive material, the photosensitive drum can provide much prolonged service life capable of performing 10,000 to 20,000 times image recording operation in case the drum has an outer diameter of 30 mm. Even though the developer toner consumption amount is dependent on the developing mode, 600 grams of the developer toners may be roughly required for conducting 10,000 times image recording operation under an employment of a single component type magnetic toners and print area ratio of 5%. In this case, the internal volume of the developing unit 5 must be 1,000 cc provided that the toners have bulk density of 0.6.
In an attempt to provide consistency between the service life of the photosensitive drum with the used-up period of the developer toners 8, the toner containing volume of the developing unit 5 must be increased. Thus, resultant processing unit becomes bulky, which in turn lower the handling ability of the processing unit and image recording apparatus must correspondingly be bulky.
To avoid this problem, an independent toner container is provided which is assembleable into the integral type processing unit. A toner container is replaceable with a new toner container by several times. Therefore, required amount of toners can be supplemented several times into the processing unit until the photosensitive drum 2 and the cleaning unit 10 reach their service lives.
Still however, the toner supplement system may provide another problems in that the toner container can be replaced with a new toner container without any restriction. Accordingly, if new toners are supplemented into the processing unit for image recording operation, whereas the photosensitive drum and the cleaning unit 10 reach their service lives. Through the image recording operation, the photosensitive drum no longer provide its photosensitivity due to fatigue of a charger wire or degradation of the photosensitive surface. Alternatively, the waste toner container 11 is full of waste toners, which in incapable of cleaning operation, otherwise the waste toner may be leaked out of the container 11, and therefore, the image recording apparatus and printing sheet may be contaminated with the waste toners.